Wire-tensioning apparatus for use in stressing concrete structures

ABSTRACT

Apparatus for tensioning members in a concrete structure including an anchor head receiving the stressing members comprises a housing adapted to be supported against the concrete structure, a hydraulically or pneumatically operated traction member adapted to reciprocate within the housing for stressing the tensioning members, a coupling device arranged at the free end of the traction member for connecting the traction member to the anchor head, means for holding the housing in position against the concrete structure, means for axial alignment of the traction member with the anchor head, and motor-driven means for rotating the coupling device when the traction member and the anchor head are aligned to produce engagement of the coupling device with the anchor head.

United States Patent WIRE-TENSIONING APPARATUS FOR USE IN STRESSINGCONCRETE STRUCTURES 8 Claims, 5 Drawing Figs.

U.S. CI 254/29 Int. Cl E2lb 19/00 Field of Search 254/29, 29 A PrimaryExaminer-Othell M. Simpson Assistant Examiner-David R. MeltonAttorney-Werner W. Kleeman ABSTRACT: Apparatus for tensioning members ina concrete structure including an anchor head receiving the stressingmembers comprises a housing adapted to be supported against the concretestructure, a hydraulically or pneumatically operated traction memberadapted to reciprocate within the housing for stressing the tensioningmembers, a coupling device arranged at the free end of the tractionmember for connecting the traction member to the anchor head, means forholding the housing in position against the concrete structure, meansfor axial alignment of the traction member with the anchor head, andmotor-driven means for rotating the coupling device when the tractionmember and the anchor head are aligned to produce engagement of thecoupling device with the anchor head.

PATENTEU AUG] 0 an SHEET 1 UF 2 WIRE-TENSIONING APPARATUS FOR USE 1NSTRESSING CONCRETE STRUCTURES The present invention relates to anapparatus for tensioning wires in a concrete structure.

Apparatus of this type usually consist of a hydraulic working cylinderhaving a piston with a continuous central bore through which the actualtraction member leads to the anchoring place. The whole apparatus isbrought to the place of use and arranged at the end of a concretestructure as precisely as possible over an anchor head of a bundle ofwires to be stressed. Thereafter the traction member is connected byhand to the anchor head, the wire or bundle of wires is stressed and theanchor head is then supported on suitable supporting members.

The present invention has for its object to provide an improvedwire-tensioning apparatus which is easy to manipulate, which operatesautomatically to a large degree and permits a rapid and safe operation,while being particularly suitable for stressing large bundles of wires.

The wire-tensioning apparatus according to the present inventioncomprises a housing adapted to be supported against one end of aconcrete structure, a tensioning unit in said housing, a traction memberextending from one end of said tensioning unit into said housing, acoupling device arranged at the free end of said traction member forconnecting said traction member to an anchor head of a wire bundle,centering means provided at said end of the traction member for axialalignment of the traction member with said anchor head, means fortemporarily connecting said housing to the concrete structure, saidconnecting means including tensioning members arranged at the outside ofsaid housing, the tensioning force of said tensioning members beingadjustable, and coupling members for said tensioning members adapted toconnect the tensioning members to the concrete structure.

In a particularly advantageous embodiment of the apparatus, thetensioning unit and the tensioning members serving as connecting meansare hydraulically or pneumatically operating working cylinders and thecoupling device for connecting the traction member to the anchor head isalso hydraulically or pneumatically operable. A central control deviceprovided with control valves is advantageously provided for controllingthe operation of the apparatus.

The invention will be described in greater detail with reference to theaccompanying drawings, in which:

FIG. 1 is a longitudinal section through an apparatus according to theinvention mounted on the end of a concrete construction, wherein theconnecting means attached to the outside of the housing have beenomitted for the sake of clearness of the drawing.

FIG. 1A is a view of one of the connecting means, here in the form ofahydraulic cylinder, which is shown in the correct position with respectto the apparatus according to FIG. 1.

FIG. 2 is a section along the line lI-II of FIG. 1, with the connectingmeans in position.

FIG. 3 is a longitudinal sectional view of the front end of amodification of the apparatus according to FIG. 1, and

FIG. 4 is a diagram of the hydraulic control means of an apparatusaccording to FIG. 1.

FIGS. 1, 1A and 2 of the drawing show different views of awire-tensioning apparatus, according to the present invention.

The main part of the apparatus consists of a housing 1, provided withlateral openings 2,3. The apparatus may be suspended on a suspensiondevice 6 of a crane cable by means of one or more links 4 and bolts 5,in order to be brought to the place of anchorage of a bundle of wires 7at the end of a concrete construction 8 to be prestressed. The baseportion of the housing 1 is supported on a thrust plate 9 at the placeof anchorage. The above-mentioned link 4 may also be formed as a ringrotatably mounted on the outside of the housing 1 and provided withbores for the bolt (see FIG. 1). The rear part of the housing 1 consistsof a hydraulic working cylinder 10, which is closed by two screwed-onend plates 11 and 12. A piston 13 can reciprocate inside the cylinder10. The piston rod 14 forms the traction member for the tensioningdevice and extends through a bore 15 in the end plate 11 forwardly tothe front part of the housing 1. The piston 13 as well as the bore 15are provided with suitable packing means 16 and 17. Two ports 18 and 19,to which pressure fluid conduits (not shown) are connected, selectivelyadmit pressure fluid to one or the other side of the piston 13 to movethe piston in one or the other direction.

The front end of the traction member 14 is supported and guided axiallyinside the housing 1 by a guide member 20. The guide member consists ofa ring 21 mounted on the traction member 14 and of a forwardlyprojecting cylindrical sleeve 22 secured to the outer edge of the ring21. The ring 21 is provided with a projection 66 engaging an axial slot67 in the housing 1 for axially guiding the member 20 and preventing anymovement of rotation thereof and of the piston rod 14 to which it issecured.

At its front end, the traction member 14 has a part 23 of enlargeddiameter forming a shoulder 23. A coupling sleeve 24 is rotatablymounted on the traction member 14 at the rear of the shoulder 23'. Whensleeve 24 abuts on the shoulder 23', it projects with its cylindricalpart 25, whose front end is provided with an internal thread 26, in thedirection of the bundle of wires to be stressed. This sleeve 24 isscrewed onto the anchor head 27 of the bundle of wires 7 to be stressed.In the illustrated embodiment the sleeve 24 is shown in the positionscrewed on the anchor head.

A centering bolt 28 is screwed into the front end of the part 22 of thetraction rod 14. This bolt cooperates with a corresponding bore 29 inthe anchor head 27 in order to bring the wire bundle 7 into the exactaxial alignment with the direction of traction.

Behind the coupling sleeve 24, a gear ring 30 and a spring washer 31 aresecured to the sleeve 24. The spring washer 31 is screwed to the sleeve24 by means of pins 32 which pass through bores 33 in the gear ring 30,whilst the gear ring 30 itself is secured with some axial clearancebetween sleeve 24 and spring washer 31. The coupling sleeve 24, the gearring 30 and the spring washer are consequently connected together andmay be rotated together about the traction member 14 and are axiallyshiftable within certain limits. One of these limits is formed by theshoulder 23' of the part 23 of the traction member 14, whilst the otherlimit is formed by the guide member 20. A helical spring 34 is arrangedbetween the front side of the guide ring 21 and the spring washer 31.The helical spring only comes into effect when the sleeve 24 is not yetscrewed onto the anchor head 27; for example when the front end of thetraction member 14 is moved into contact with the anchor head 27, thespring 34 will abut against a baseplate 35 on the ring 21 and at thesame time against the spring washer 31, and will thereby press thecoupling sleeve 24 with a predetermined force against the anchor head 27provided with an external thread 36. When the sleeve 24 is now correctlyrotated, the two threads 26, 36 can engage one another and the sleeve 24may be screwed on the head 27. As soon as the thread of the sleeve 24has engaged the thread of the head 27, the function of the spring 34 isterminated.

In the represented apparatus the coupling sleeve 24 is screwed onto theanchor head 27 automatically by means of a motor. To this end the gearring 30 is driven by a pinion 37. The pinion 37 is mounted on a splinedshaft 38 for rotation therewith and axial movement along the shaft whichis mounted in the housing and is driven in one or the other direction byan oil engine 39 via a chain and chain wheels 40, 41. The pinion 37penetrates through a recess 68 in thesleeve 22 of the guide member 20which is secured against rotation. Due to the axial mobility the pinion37 can move together with the gear ring 30 and the traction member 14,to any position along the path of reciprocation of the traction member14.

A pointer 42 projects outwardly through the housing 1 from the sleeve 22and moves along a graduated scale 43. This enables the position of thetraction member 14 to be ascertained or the path of stress applied tothe wire bundle to be read at any time.

In order to secure the apparatus to the concrete construction, fourhydraulic anchoring cylinders 44, 45, 46, 47 are, in the embodimentshown, mounted on the outside of the housing 1 between suitable bearingplates 48, 49, 50 and 51 and four identical bearing plates of which onlythe plate 48 is visible in FIG. 1A.

Holding pins 52 are screwed into the thrust plate 9 on the concreteconstruction 8. A front plate 53 of the housing 1 provided with openings69 is pushed over the pins 52. The piston rod 54 projects from thecylinder 44 towards the pin 52 and carries a coupling sleeve 55 at itsfront end. For connecting the piston rod to the pin 52, the sleeve 55 ispushed over the pin 52 up to a shoulder 56, and then a key 55 is pushedthrough corresponding perforations in sleeve 55 and pin 52.

Due to the holding cylinders 4447, at least two of which should beprovided, the stressing apparatus may be applied and securely attachedto the concrete construction 8 before starting a stressing operation.When the traction member 14 is pressed against the anchor head 27,before effecting coupling of the sleeve 25 with the anchor head 27, theholding force of the cylinders .44 to 47 may be overcome, and theapparatus may be aligned with respect to the anchor head 27 which isinclined as the case may be, so that the sleeve 24 may be screwed ontothe head 27. As the wire bundles are being stressed, the apparatus thenstraightens up again. The same applies when the sleeve 24 is releasedfor the purpose of disconnecting the sleeve 24 from the anchor head 27.

FIG. 3 f the drawing shows diagrammatically a modification of thecoupling device at the front end of the traction member 14. An extension60 is screwed into the coupling sleeve 57, which abuts on the shoulders58 of a stop ring 59 screwed onto the traction member 14. The extension60, formed as a sleeve, has such an external diameter that it can engagethrough the bore 61 of the thrust plate 9 into a recess 62 provided inthe concrete construction 8 in order to grip the anchor head 63 of abundle of wires located in the recess. Here, too, the traction member14, has a centering bolt 64, which may penetrate into a bore 65 of thehead 63.

The extension 60 is internally threaded at its front end and may bescrewed onto the anchor head 63 by rotating the sleeve 57. The sleeve 57is driven in exactly the same way as the sleeve 24 of the apparatusshown in FIG. 1.

FIG. 4 of the drawing shows a hydraulic diagram, in zero position, forthe automatic drive of a stressing apparatus according to the invention.

A high-pressure pump unit 101 comprises an electromotor 102 for ahigh-pressure pump 103, a relief valve 104, a relief valve 105, and anoil filter 106 with associated conduits. A and B are pressure fluidconnections, T is a return conduit, S a suction pipe and 133 a checkvalve.

107 designates the actual control device with the different controlvalves 108, 109, 110 and 111. Each control valve may be brought into oneof the three schematically indicated operating positions, as desired.Relief valves 112, 113, 114, 115, 116 and 117, pressure gauges 118, 119,120, 121, 122 and 123, as well as nonreturn valves 124 and 125 whosefunctions may be seen from the diagram are provided in the variousconduits.

134 indicates the actual stressing device which is provided with twoholding presses or cylinders 126, 126, as well as with a stressing pressor cylinder 127. The stressing cylinder is associated with a throttlevalve 128, a check valve 129 and a pressure gauge 130. 132 is a reliefvalve. Finally, 131 designates the oil engine for rotation in one or theother direction of the coupling sleeve of the traction member of thestressing apparatus.

An operating cycle of the automatic stressing apparatus is explained indetail hereinbelow:

The stressing apparatus together with the control device 107 issuspended from a cable and is brought near the place of anchoring of thewire bundle in the concrete construction 8 to be prestressed.

The control device 107 is brought into a position from which thestressing procedure can easily be controlled and supervised. Thepressure gauge 130 as well as the path indicator 42, 43 must be easilyvisible.

The various conduits of the pump unit 101 are connected to the controldevice 107 and the pump 103 is set into operation.

The four holding pins 52 are screwed into the thrust plate 9. Thehousing 1 of the stressing apparatus is pushed over the holding pins 52and provisionally secured.

The pistons 54 of the four holding cylinders 4447 are extended untilthey abut on the shoulders 56 of the pins 52. Then the keys 55 areinserted and the holding cylinders are pressurized until the housing 1abuts tightly on the thrust plate 9.

The traction member 14 is moved forwards and pressed against the anchorhead 27. Indicator 42 and scale 43 are set to 0 (zero).

The coupling sleeve 24 is then screwed onto the head 27 until it abutsagainst the head.

The throttle valve 128 is then closed and the actual stressing of thewire bundle is begun. Up to a certain pressure, operation can beeffected via the rapid oil feed, then a switchover takes place to thelower speed. The oil pressure in the stressing cylinder may be read onthe pressure gauge 130, and by means of a calibration curve, thetensional force can be determined.

The pressure gauge 121 in the control device serves thereby as control,so long as oil is pumped into the cylinder.

The elongation may be read directly from the scale 43.

After the maximum tensional force is reached, the necessary size orheight of the supports for the anchor head 27 may be read from thescale.

Fixing clamps are placed in the housing 1 in predetermined positions andthe support members are arranged by means of electromagnetic grippers.

By opening the throttle valve 128, the anchor head 27 is placed on thesupport members.

Then the holding cylinders 4447 are briefly placed under pressure inabutting pressure direction, the traction member 14 is applied againstthe anchor head 27 and the coupling sleeve 24 is released and unscrewed.

The fixing clamps for the support members are removed.

Then the traction member 14 is withdrawn until this latter is fullydisconnected from the anchor head 27, and the holding cylinders 4447 arereleased from the holding pins 52.

The stressing apparatus is now ready for the next stressing operation.

When the stressing apparatus is to be used for stressing the wire bundleabove the normal stressing path, it will become necessary to useextensions for positioning the housing 1 further away from the concreteconstruction.

To this end, the anchor head 27 will be temporarily supported.

Then the holding cylinders 4447 are released from the pins 52. By urgingthe traction member 14 forwardly, the housing 1 of the apparatus movesaway from the concrete construction. The housing is moved for such adistance that a gap will be formed between the front end of the housing1 and the thrust plate 9, which gap is somewhat greater than theextensions to be inserted.

Now the said extensions are placed on the four pins 52.

The housing is then pressed against the extensions and the fixing clampsfor the support members are arranged in position.

The holding cylinders 4447 are again attached and the second stage ofthe stressing operation may begin.

The temporarily arranged support members for the anchor head 27 areremoved and replaced by the final, longer support members.

We claim:

1. Wire-tensioning apparatus for use in stressing concrete structurescomprising a housing adapted to be supported against one end of aconcrete structure, a tensioning unit in ranged at the free end of saidtraction member for connecting said traction member to an anchor head ofa wire bundle, centering means provided at said end of the tractionmember for axial alignment of the traction member with said anchor head,means for temporarily connecting said housing to the concrete structure,said connecting means including tensioning members arranged at theoutside of said housing, the tensioning force of said tensioning membersbeing adjustable, and coupling members for said tensioning membersadapted to connect the tensioning members to the concrete structure.

2. Apparatus according to claim 1, in which said stressing unitcomprises a hydraulic or pneumatic working cylinder, a pistonreciprocating in the cylinder, and a piston rod forming a tractionmember projecting into said housing, said coupling device arranged atthe free end of the traction member including an internally threadedcoupling sleeve mounted to rotate on the traction member.

3. Apparatus according to claim 1, in which means are provided for theremote control of said coupling device connecting the anchor head of awire bundle to said traction member.

4. Apparatus according to claim 3 and comprising motordriven means forselectively rotating said coupling sleeve in one or the other direction.

1 said anchor head.

5. Apparatus according to claim 4, in which said motordriven meanscomprises a gear'ring which may be brought into driving connection withsaid coupling sleeve, a driving pinion for said gear ring, said pinionbeing mounted for rotation on a shaft and axially movable therealong,which shaft extends parallel to the traction member of said tensioningunit, and a driving motor for said shaft.

6. Apparatus according to claim 1, in which said tensioning membersattached to the outside of the housing comprise hydraulic or pneumaticworking cylinders, having pistons to transmit the tensioning force.

:7. Apparatus according to claim 1, in which said centering meanscomprise a forwardly projecting centering pin arranged in the center ofthe front end of said traction member, said centering pin being adaptedto engage a central opening in 8. Apparatus according to claim 1, inwhich said tensioning unit and said tensioning members arranges at theoutside of the housing are hydraulically or pneumatically operatedworking cylinders, said coupling device for the anchor head being alsohydraulically or pneumatically operable, and a central control deviceprovided with control valves being provided for controlling theoperation of the apparatus.

1. Wire-tensioning apparatus for use in stressing concrete structurescomprising a housing adapted to be supported against one end of aconcrete structure, a tensioning unit in said housing, a traction memberextending from one end of said tensioning unit into said housing, acoupling device arranged at the free end of said traction member forconnecting said traction member to an anchor head of a wire bundle,centering means provided at said end of the traction member for axialalignment of the traction member with said anchor head, means fortemporarily connecting said housing to the concrete structure, saidconnecting means including tensioning members arranged at the outside ofsaid housing, the tensioning force of said tensioning members beingadjustable, and coupling members for said tensioning members adapted toconnect the tensioning members to the concrete structure.
 2. Apparatusaccording to claim 1, in which said stressing unit comprises a hydraulicor pneumatic working cylinder, a piston reciprocating in the cylinder,and a piston rod forming a traction member projecting into said housing,said coupling device arranged at the free end of the traction memberincluding an internally threaded coupling sleeve mounted to rotate onthe traction member.
 3. Apparatus according to claim 1, in which meansare provided for the remote control of said coupling device connectingthe anchor head of a wire bundle to said traction member.
 4. Apparatusaccording to claim 3 and comprising motor-driven means for selectivelyrotating said coupling sleeve in one or the other direction. 5.Apparatus according to claim 4, in which said motor-driven meanscomprises a gear ring which may be brought into driving connection withsaid coupling sleeve, a driving pinion for said gear ring, said pinionbeing mounted for rotation on a shaft and axially movable therealong,which shaft extends parallel to the traction member of said tensioningunit, and a driving motor for said shaft.
 6. Apparatus according toclaim 1, in which said tensioning members attached to the outside of thehousing comprise hydraulic or pneumatic working cylinders, havingpistons to transmit the tensioning force.
 7. Apparatus according toclaim 1, in which said centering means comprise a forwardly projectingcentering pin arranged in the center of the front end of said tractionmember, said centering pin being adapted to engage a central opening insaid anchor head.
 8. Apparatus according to claim 1, in which saidtensionIng unit and said tensioning members arranges at the outside ofthe housing are hydraulically or pneumatically operated workingcylinders, said coupling device for the anchor head being alsohydraulically or pneumatically operable, and a central control deviceprovided with control valves being provided for controlling theoperation of the apparatus.